Can you help me with this problem

System:
 

x+y=11

x=11-y then 11-y+1.75y=14
0.75y=14-11=3
y=4 - orange juice
x=11-4=7 - apple juice

if you wanna use a graphic method you should draw the lines of each equation. The intersection of these lines is solution

Num of plants = (original#ofplants)*(1.6)^t

Just tell koda to adjust the number of shapes himself.